REGRESSION OF SENSORY ANESTHESIA DURING CONTINUOUS EPIDURAL INFUSIONSOF BUPIVACAINE AND OPIOID FOR TOTAL KNEE REPLACEMENT

The epidural administration of morphine and fentanyl delay the regress ion of sensory anesthesia in postoperative patients receiving epidural bupivacaine. This study was performed to determine any differential e ffects of two lipid-soluble opioids upon regression of sensory anesthe sia during coadministration with epidural bupivacaine. Forty-eight pat ients scheduled for total knee replacement underwent lumbar epidural c atheterization and received 1.5% etidocaine with 1:200,000 epinephrine to establish sensory anesthesia to approximately T6 bilaterally. Pati ents were randomized by the investigational pharmacy to receive either : (a) bupivacine without opioid (control) (n = 16), or (b) bupivacaine with 1 mg/mL of meperidine (n = 16), or (c) bupivacaine with 3 mug/mL of fentanyl (n = 16) in a double-blind fashion. Intraoperatively, 0.5 % bupivacaine +/- opioid was administered by epidural infusion at a ra te of 10 mL/h. Postoperatively, the bupivacaine concentration was decr eased to 0.25% (+/- the same opioid), and the infusion rate was decrea sed to 4 mL/h. Pinprick sensory anesthesia and verbal numerical pain s core were recorded each hour after surgery by a blinded investigator. For each patient, the study was considered terminated when the cephala d level of sensory anesthesia bilaterally decreased five dermatomal se gments or the pain score reached ''5'' (moderate pain). Patients recei ving epidural infusions of bupivacaine and meperidine had a significan tly slower regression of sensory anesthesia and slower development of pain. There was no difference in the rate of regression of sensory ane sthesia or the development of pain among patients receiving bupivacain e alone or bupivacaine with fentanyl.